Methods for correcting deviations in preplanned tooth rearrangements

ABSTRACT

Orthodontic treatment is achieved using a series of successive, removable repositioning appliances, such as thin polymeric shell appliances referred to as aligners. A set of aligners is originally provided to the patient. If the patient&#39;s treatment goes off course using the original set of aligners, further aligners are designed and fabricated to move the deviant tooth arrangement back to a target tooth arrangement which was part of the original treatment program.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 09/843,247, filed Apr. 25, 2001 now U.S. Pat. No. 6,488,449,which claims the benefit under 37 CFR §1.78(a)(3) of prior provisionalapplication No. 60/199,465, filed on Apr. 25, 2000, the full disclosuresof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to a method of repositioning teeth foruse in orthodontic treatment. Particularly, this invention relates tothe use of orthodontic appliances for producing tooth movements. Moreparticularly, this invention relates to the use of a plurality ofelastic repositioning appliances for producing such tooth movements.

Orthodontic treatments involve repositioning misaligned teeth andimproving bite configurations for improved cosmetic appearance anddental function. Repositioning teeth is accomplished by applyingcontrolled forces to the teeth over an extended period of time. This isconventionally accomplished by wearing what are commonly referred to as“braces.” Braces comprise a variety of appliances such as brackets,bands, archwires, ligatures, and O-rings. After they are bonded to theteeth, periodic meetings with the orthodontist are required to adjustthe braces. This involves installing different archwires havingdifferent force-inducing properties or by replacing or tighteningexisting ligatures. Between meetings, the patient may be required towear supplementary appliances, such as elastic bands or headgear, tosupply additional or extraoral forces.

Although conventional braces are effective, they are often a tedious andtime consuming process requiring many visits to the orthodontistsoffice. Moreover, from a patient's perspective, they are unsightly anduncomfortable. Consequently, alternative orthodontic treatments havedeveloped. A particularly promising approach relies on the use ofelastic positioning appliances for realigning teeth. Such appliances maycomprise a thin shell of elastic material, referred to as an “aligner”,that generally conforms to a patient's teeth but is slightly out ofalignment with the initial tooth configuration. Placement of an alignerover the teeth applies controlled forces in specific locations togradually move the teeth into the new configuration. Repetition of thisprocess with successive appliances comprising new configurationseventually move the teeth through a series of intermediate arrangementsto a final desired arrangement. A full description of an exemplaryelastic polymeric positioning appliance is described in U.S. Pat. No.5,975,893, and in published PCT application WO 98/58596 which designatesthe United States and which is assigned to the assignee of the presentinvention. Both documents are incorporated by reference for allpurposes.

Systems of preformed aligners employing technology described in U.S.Pat. No. 5,975,893, are commercially available from Align Technology,Inc., Santa Clara, Calif., under the tradename Invisalign® System. AlignTechnology, Inc., is the assignee of the present application. TheInvisalign® System relies on designing and fabricating at least most ofthe aligners to be worn by the patient at the outset of treatment. Thedesign of the aligners relies on computer modeling of a series ofsuccessive tooth arrangements, and the individual aligners are designedto be worn over the teeth and to elastically reposition the teeth toeach of said tooth arrangements. Usually, the set of aligners which isdesigned and fabricated at the outset of the treatment is able tosuccessfully reposition the teeth to a final desired arrangement. Insome cases, however, the treatment deviates from the planned movementstages making continued treatment with the previously provided set ofaligners difficult or impossible. Such deviations can arise frombiological variations in the individual patient, poor patientcompliance, or other factors. The deviations will usually becomeapparent when the next aligner to be worn in the set of successivealigners does not fit. A poor fit indicates that the tooth arrangementhas not progressed to the desired intermediate stage and that the teethare not ready for the next aligner.

When such deviations occur, the response has usually been to start overwith whatever actual tooth arrangement that has been received being thestarting point. Aligners are then planned and fabricated to bring theteeth from the actual intermediate arrangement to the desired finalarrangement, which is usually the same final arrangement as was thetarget of the original set of aligners. Starting over, however, can beinefficient and wasteful. Relatively large numbers of aligners can berequired, and the remaining aligners in the original set will usually bewasted.

For these reasons, it would be desirable to provide alternative and/orimproved methods for making mid-course corrections in orthodontictreatment utilizing sets of aligners or other repositioning applianceswhich are removable and successively worn by a patient to effect acourse of orthodontic treatment. It would be particularly desirable ifsuch methods did not require disposal of all or some of the alignersfrom the original set and were relatively easy to implement with minimumpatient inconvenience. At least some of these objectives will be met bythe inventions described hereinafter.

2. Description of the Background Art

U.S. Pat. No. 5,975,893, and published PCT application WO98/58596, havebeen described above. U.S. Pat. No. 6,454,565, relates to thefabrication of orthodontic aligners having varying elastic moduluses.The full disclosures of each of these patents and pending applicationsare incorporated herein by reference.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, an improved method for repositioningteeth is provided. The method for repositioning generally relies on useof an original set of removable positioning appliances, typicallyaligners as described in U.S. Pat. No. 5,975,893, the full disclosure ofwhich has been previously incorporated herein by reference. The alignersor other appliances are shaped to move teeth through a plurality ofpredetermined successive arrangements corresponding to the shape of eachappliance. That is, the appliances will be configured to applyrepositioning forces to the teeth so that the teeth are moved to anarrangement which closely conforms to the unstressed geometry of thealigner. Thus, after a patient has completed wearing any individualaligner or other appliance, it will be expected that the tootharrangement will match the shape of the aligner or appliance and thatthe teeth will be ready to receive a next successive aligner or otherappliance. The next successive aligner will be shaped slightlydifferently from the immediately prior aligner, and it is thisdifference in shape that will move the teeth still further to their nextarrangement. Wearing of successive aligners or other appliances thus caneffect an entire course of orthodontic treatment as the teeth are movedthrough a series of predetermined successive arrangements.

In the case of the Invisalign® System, an original set of aligners willbe designed and fabricated at the outset of treatment. The individualaligners will then be available to the patient and/or treatingprofessional so that the aligners may be worn and exchanged as the teethprogress through the expected successive arrangements. Usually, eachindividual aligner is worn for about two weeks corresponding to onestage of treatment. This period, of course, can vary from several daysto several weeks or longer, depending on the individual treatment planselected for the patient.

The present invention is concerned with those patients who do notprogress through treatment as expected and planned. In some cases, anactual tooth arrangement achieved by a patient will differ from theexpected tooth arrangement corresponding to the shape of a particularappliance. Such deviation from the expected treatment will usuallybecome apparent when the patient tries to wear the next aligner in aseries. If the actual tooth arrangement differs to any significantdegree from that which was expected, the next aligner in series willtypically not be able to seat properly over the teeth. Such inability tofit or seat on the teeth provides an indication that the actual tootharrangement which has been achieved at that point in treatment differsfrom the expected tooth arrangement which should have been achievedafter treatment with the immediately prior appliance.

The present invention provides methods for correcting such deviations inthe planned and expected treatment path by providing at least oneadditional removable appliance which has a shape or a complianceselected to move the teeth from the actual (but deviant) tootharrangement back to one of the predetermined successive tootharrangements. The tooth arrangement to which the teeth are reconfiguredwill often be the arrangement to which they should have been at the endof the just completed stage. Alternatively, the arrangement could be anyone of the successive stages, usually five stages or fewer beyond thejust completed stage, more usually four stages or fewer, and typicallyno more than three stages beyond the just completed stage.

For the most minor deviations, it will be often be sufficient to providean aligner or other tooth positioning appliance which has the samegeometry as an aligner from the original set, usually as the nextaligner in the series. While the aligner will have the same shape, itwill be more compliant or elastic so that it can fit and seat over theteeth, even though the shape is further from the geometry of the actualtooth configuration than had been originally intended. The morecompliant aligner can then bring the teeth back toward the targetconfiguration for that stage of treatment. Optionally, two or morecompliant aligners having the same geometry could be employed, wheresuccessive ones of the new aligners will be incrementally stiffer ormore rigid to continue to move the teeth toward the targetconfiguration.

The use of additional aligners having the same shape as an originalaligner, but which are more compliant, is particularly advantageoussince it simplifies design and fabrication of these aligners. The shapeor geometry of the aligner would already have been planned during theinitial treatment planning process (as described in detail in priorpatent U.S. Pat. No. 5,975,893, which has been incorporated herein byreference), and it is necessary only to mold or otherwise fabricate thealigner out of materials having different elasticities. The ability toform aligners having different elasticities is described in detail inco-pending application Ser. No. 09/616,830, related to U.S. Pat. No.6,454,565, the full disclosures of which have previously beenincorporated herein by reference.

In some instances, however, it may not be possible and/or desirable touse aligners having the same geometry as an original aligner to bringthe teeth back on to the intended treatment path. In such cases, it willbe necessary to design one or more aligners having different shapes inorder to move the teeth back from their actual configuration to a tootharrangement corresponding to one of the appliances from the original setof appliances. Such treatment planning can be performed, for example, bythe methods used for the original treatment planning as described inU.S. Pat. No. 5,975,893, the full disclosure of which has beenincorporated herein by reference. That is, the actual tooth arrangement,i.e., the tooth arrangement which has been actually achieved in thetreatment thus far, will be digitally modeled. Based on the digitalmodel of the actual tooth configuration as a starting point, and aselected one of the target intermediate stages as an ending point, aseries of one, two, three, four, or five, or more, new aligners or otherpositioning appliances can be designed using the computer-aided designprotocols described in the patent. Once the new aligner designs arefinalized, the digital models of the aligners can be used to fabricateactual aligners using the previously described methods.

For both compliant aligners and differently shaped aligners, the patientwill wear the corrective aligners until the teeth have returned to anarrangement which allows an aligner from the original set of aligners tobe worn and to move teeth to the next successive arrangement. Dependingon the degree of deviation, it may take one, two, three, four, five, oreven more, additional aligners or other positioning appliances toprovide the desired correction. The corrective aligners or otherappliances might be worn from several days to several weeks, or more,until the desired correction is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an aligner according to the present invention andshows how the aligner is placed over a patient's teeth.

FIGS. 2-4 illustrate an exemplary series of three successive tootharrangements which may be achieved with the aligners of FIG. 1.

FIG. 5 is a decision tree illustrating an exemplary method according tothe present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

The present invention relies on the use of aligners 100 for positioningteeth in a tooth arrangement TA, as illustrated in FIG. 1. The aligneris a thin shell polymeric appliance of the type commercially availableas part of the Invisalign® System available from Align Technology, Inc.,Santa Clara, Calif. The planning and fabrication of such aligners isdescribed in detail in issued U.S. Pat. No. 5,975,893, the fulldisclosure of which has previously been incorporated herein byreference. The aligners 100 are worn by a patient over the tootharrangement for a sufficient time to rearrange the teeth to a desiredsubsequent tooth arrangement. A plurality of successive aligners areworn until an entire course of the treatment is completed.

As shown in FIGS. 2-4, multiple stages of treatment will result in theteeth being rearranged. Tooth arrangement 200 shows the teeth in aninitial configuration with significant misalignment. Tooth arrangement202 shows the teeth of arrangement 200 partially reconfigured. Finally,tooth arrangement 204 illustrates the teeth in a desired finalconfiguration. The methods for tooth arrangement of the presentinvention will typically rely on many more than three stages to achievea desired reconfiguration. Usually, at least three stages will berequired, more usually, at least five stages will be required, andtypically 20 or more stages may be utilized.

If at any time during the originally planned course of treatment, thetooth arrangement deviates from a desired intermediate stage, i.e., anintermediate configuration is not achieved, it may be desirable toemploy the methods of the present invention to correct such deviationand reconfigure the tooth arrangement to a desired predeterminedintermediate stage. As shown in FIG. 5, the patient is initially treatedwith an original set of tooth aligners. The patient wears individualaligners from the original set to reposition teeth to subsequentpredetermined tooth arrangements. Periodically during treatment, thepatient or treating professional will observe the actual tootharrangement achieved at any stage of treatment to see if it issatisfactory. If the progress is satisfactory, the patient will thenwear the next aligner in the predetermined set of aligners. The processof confirming satisfactory progress and moving on the next tooth alignermay be repeated until the final desired tooth arrangement is achievedand the treatment ends.

In the case of some patients, however, the progress being achieved willnot be satisfactory. For example, the next aligner in the predeterminedoriginal set of aligners may not seat or fit properly, indicating thatthe teeth have not moved to their desired target intermediatearrangement. In such cases, the present invention will provideadditional aligner(s) or other reposition appliances to move the teethback to an arrangement which was part of the original treatment path.The patient will then wear the additional aligner or aligners until theteeth are returned to the original treatment plan. If for any reason theuse of the additional aligners is unsatisfactory, it may be appropriateto design and fabricate still further aligners or sets of aligners inorder to correct the deviant treatment path. Once the teeth have beenreturned to an arrangement on the desired treatment path, treatment maythen continue with the original aligner set which had been provided tothe patient at the outset of treatment.

While the above is a complete description of the preferred embodimentsof the invention, various alternatives, modifications, and equivalentsmay be used. Therefore, the above description should not be taken aslimiting the scope of the invention which is defined by the appendedclaims.

What is claimed is:
 1. In a method for repositioning teeth using anoriginal set of removable positioning appliances shaped to move teeththrough a plurality of predetermined successive arrangementscorresponding to the shape of each appliance, a method for correctingmidcourse deviations from the successive arrangements comprising:determining that an actual tooth arrangement of a patient differs froman expected tooth arrangement corresponding to the shape of a particularappliance; and providing at least up to five additional removableappliances each of which have a shape or a compliance selected to movethe teeth from the actual tooth arrangement back to one of thepredetermined successive tooth arrangements.
 2. A method as in claim 1,wherein determining comprises observing whether a particularpredetermined removable appliance fits over the teeth at the expectedcorresponding tooth arrangement.
 3. A method as in claim 1, whereinproviding comprises providing removable positioning appliances whichhave the same shape as an appliance from the original set but which aremore compliant, wherein the more compliant appliances can be fitted overthe teeth to move the teeth back to one of the predetermined successivearrangements.
 4. A method as in claim 1, wherein providing comprisesproviding removable positioning appliances which have a shape differentfrom the original appliances, wherein the shape is selected to move theteeth from their actual arrangement back to one of the predeterminedsuccessive arrangements.
 5. A method as in claim 1, wherein providingcomprises providing at least one appliance which has a shape the same asan appliance from the original set but which is more compliant and atleast one appliance which has a shape different from the originalappliances selected to move teeth back to one of the predeterminedsuccessive arrangements.